1. Field of the Invention
The present invention generally relates to a security technique and more particularly to an electronic device and a program enabling detection of unauthorized operations performed on a removable storage medium during a power-saving state by confirming validity of data in the storage medium upon returning from the power-saving state.
2. Description of the Related Art
With the increasing energy-saving consciousness in recent years, electronic devices such as copiers, printer devices, multi-function devices (MFP), personal computers (PC), and the like, are controlled to shift to various types of energy-saving modes in which power supply to each element of hardware in the electronic devices is stopped after detecting an idle state for a certain period of time or a time range set in advance. For example, the multi-function devices control a status of electric power at a heater power source to a fuser for a print process, a motor power source to a spindle of a hard disk, and a panel power source to a touch panel, and power supply to each device of an engine controller and a main controller. Power-saving modes having various levels of power supply have been prepared.
Examples of the above-mentioned power-saving modes include an STR (Suspend to RAM) mode for stopping power supply to almost all devices such as a CPU, hard disk, and the like on the main controller while a current operation state is stored in a memory, a controller off mode for stopping the power supply to an entire portion of the main controller further including the memory, and the like. When the multi-function devices have shifted to these power-saving modes, the power-saving modes are released through touch panel operation by an operator and data reception via a network or an interface. Then, the power supply to each element of hardware is resumed and the multi-function devices return to a normal stand-by mode.
In terms of energy saving, preferably, the power-saving modes sequentially shift to a lower level of power supply in accordance with an operation state of the electronic devices. On the other hand, when electronic devices have shifted to the power-saving mode, the power supply to each element of hardware is sequentially stopped. Accordingly, as the level of power supply becomes lower, time for returning is increased, for example, and this poses a problem in that usability for a user is reduced. Further, in recent years, problems in terms of security resulting from the power-saving modes have become evident. In the following, the problems in terms of security are described.
In electronic devices of recent years such as multi-function devices, programs and user data are stored in a removable storage medium such as a Secure Digital memory card (hereafter referred to as an SD card) and these application programs are read from the storage medium so as to add, update, and expand functions of applications or the user data is read so as to use it in the application, for example. However, it is possible to expand functions through easy operation, so that the storage medium may be used in plural multi-function devices. In view of this, it is necessary to take measures for security so as to prevent unauthorized use.
For example, with the purpose of providing an image forming apparatus capable of readily preventing use of an insertable storage medium in plural devices and a method for stopping a program, Japanese Laid-Open Patent Application No. 2004-46801 (Patent Document 1) discloses an image forming apparatus including a program performing a process using hardware resources and a slot capable of inserting and removing a storage medium. The image forming apparatus also includes a status monitoring unit monitoring insertion and removal of the storage medium for the slot, a storage medium starting unit enabling access of the storage medium inserted into the slot and disabling access of the storage medium removed from the slot, and a program starting unit stopping the program read and started from the storage medium upon receiving notification of removal of the storage medium from the slot while reading and starting the program from the access-enabled storage medium.
Patent Document 1: Japanese Laid-Open Patent Application No. 2004-46801
FIGS. 1A and 1B show examples of operation state of a software unit controlling removable storage media (SD cards, for example) in a normal standby mode (FIG. 1A) and a controller off mode (FIG. 1B). As shown in FIG. 1A, in the standby mode in which a CPU and an SD card slot are supplied with sufficient electric power on a main controller, a kernel of an operating system (OS) and each software unit are expanded in a memory area under control of the CPU and are in an operating state. Accordingly, installation and removal of the SD card from the slot are detected through monitoring by the software unit and it is possible to perform a process in accordance with the installation and removal of the SD card.
By contrast, when the power supply to the CPU is stopped as in the controller off mode, for example, as shown in FIG. 1B, the software unit controlling the SD card slot is stopped, so that it is impossible to detect the installation or removal of the SD card. In the same manner, while the power supply to the SD card slot is stopped, even if the software unit is in the operating state, it is impossible to detect the installation and removal of the SD card.
In other words, in the above-mentioned conventional technique, when electric power is sufficiently supplied to hardware such as the control unit (CPU), the slot capable of installing and removing the storage medium, and the like on the main controller (standby mode or other power supply mode having a high level of power supply), it is possible to detect the installation and removal of the storage medium. However, in those power supply modes such as the above-mentioned STR mode and the controller off mode in which the power supply to the control unit or the slot is stopped, it is impossible to detect the installation and removal of the storage medium.
Further, in those power supply modes in which the power supply to the control unit or the slot is stopped, it is impossible to detect the installation or removal of the storage medium, so that even if the storage medium is removed during the power supply mode, it is impossible to detect the removal operation when the storage medium is installed on the slot again before returning. In other words, other than the above-mentioned use of the storage medium in plural devices, there are problems in that there is a possibility that a third person with malicious intention may perform unauthorized operations such as altering or stealing of contents stored in the storage medium during the power supply mode and there is a risk of inducing abnormal operation or abnormal end of an active application or an electronic device. User data on an address book and the like is not protected using electronic authentication in many cases, so that there is a problem in that altered user data may be used without being noticed by the user and important business information may be transferred via facsimile or as a file to an erroneous destination.